1. Field of the Invention
The present invention generally relates to a copper-based catalyst for converting ammonia (NH3) into nitrogen and, more particularly, to a copper-based catalyst with better selectivity and suitable for converting ammonia (NH3) of high concentration.
2. Description of the Related Art
Waste resin generated by industries can be wet treated to produce ammonia with concentration up to 66.7%. Ammonia can be decomposed by a catalytic decomposition method. There are two kinds of catalytic decomposition methods for ammonia, which are reduction reaction and oxidation reaction. The reduction decomposition method mainly produces hydrogen and nitrogen, but is energy-waste due to its high reaction temperature. The oxidation decomposition method mainly produces nitrogen and water. Nitrogen produced by the oxidation decomposition method may react with oxygen, convert into nitride oxides as nitric oxide, nitrogen dioxide, or nitrous oxide, thereby becoming a pollution source of the natural environment.
To solve the problems resulting from the catalytic decomposition of ammonia, industries make an utmost effort to develop various catalysts. For instance, a conventional platinum/copper oxide/aluminum oxide (Pt/CuO/Al2O3) catalyst with selectivity is used in a decomposition process of ammonia, by which produces vapor mainly containing nitrogen and water. However, as long as the reaction temperature of the process increases, nitrogen produced in the process tends to react with oxygen, thereby converting into nitride oxides as nitric oxide, nitrogen dioxide, or nitrous oxide. In addition to nitride oxides as the pollution sources produced in the process, the conventional platinum/copper oxide/aluminum oxide, catalyst is also a catalyst with higher cost. Therefore, it is necessary to further improve the conventional platinum/copper oxide/aluminum oxide catalyst.
In Taiwan patent No.I259782, an activated fiber, a furnace stone or a furnace stone powder is used as a porous support. The porous support has a copper or a cuprate as a catalytic center, and is converted into a conventional catalyst by ion exchange and calcination. Although the conventional catalyst has decomposition conversion of ammonia up to 90%, only 85% of nitrogen produced by the conventional catalyst can be exhausted as nitrogen form. As a result, the remained nitrogen will convert into nitride oxides, thereby becoming pollution sources and generating awful effect to natural environment.
Moreover, noble metal as platinum, palladium, ruthenium, iridium or silver is used as a conventional catalyst. The easily oxidized noble metal converts ammonia into nitrogen under lower temperature. However, the conventional catalyst with noble metal has a higher cost, thereby decreasing the economic benefit of processing the waste.
In light of this, it is necessary to develop a copper-based catalyst differing from the conventional catalysts and suitable for selectively decomposing ammonia into nitrogen to solve the problems discussed above.